Chromatography Forum

In the near future, my lab will be purchasing either an evaporative light scattering detector (ELSD) or a charged aerosol detector (CAD). I have worked extensively with a Sedere Sedex 85LT ELSD; but, have not worked with CAD.

Are there any pros and cons of each detector type?

We have both of these in my lab. I prefer the Alltech ELSD 3300 as its more robust and less prone to flooding, the CAD easily floods as its waste is on a gravity suction line which means if it overflows or you run out of nitrogen in the middle of a run it goes back into the machine and costs a fortune to fix (last time £1000 for a small electronics board helpfully designed to be right next to the bit the flood will start for obvious reasons by the single manufacturer as they are the only ones who produce the parts!).

Both function well but we work with high levels of salt in our samples and the CAD doesnt cope, the ELSD copes a bit better. I also find the CAD if it gets a big signal contaminant (like our salts) it takes far longer for the baseline to settle than the ELSD too.

You cant alter the CAD baseline parameter/conditions, you can with the ELSD.

The ELSD can work with gradients and switch methods, the CAD just about copes with very gentle gradients but can't handle switches as the baseline takes too long to settle.

Given the cost as well of the detectors (8k for used ELSD vs. 25k for used CAD!) if you can use either I'd definately stick with the ELSD given my experiences!

p.s. We also tested an NQAD (nano quantity analyte detector) and found it performs similarly to the CAD but with slightly increased sensitivity (LOD ~0.6ppm) and had less problems with a gradient, although again not as good as the ELSD.

lynz x

for the most cases we have dealt on this matter we have always found the CAD to be very much superior in LOD, LOQ capacity
if it is something important to you then it is worth the money
if lower limit of detection is not the matter for you then ELSD will be simpler to use and cheaper

another question is if you intend to have simply the detector put on an existing HPLC or you are going to buy a new system?
this is also a question, with a complete system you always get a complete support,
no excuse from the HPLC or detector techs that it is the other side fault. it is important when your system is down and nobody cares to fix it for you

I found CAD about 5x lower LOD than Alltech 3500 and Sedex 85 but about 4x higher cost. 2nd poster said $25K
but I believe the current list for CAD is over $40K.

Thank you to all who offered well thought and very valuable advice. Your time and consideration are most appreciated!

Also, do you know if the Alltech ELSD 3300 is better at not flooding than the Sedere Sedex 85LT?

We have Sedere 55 and 75 as well as Alltech 800. I personally like Sedere better due to sensitivity, easy maintenance and reliability. We are using them everyday with no problem. We are keeping separate systems for TFA and ammonium formate/acetate in order to avoid long equilibration and baseline noise.

I have both Sedex 85 and Corona ultra in the lab. There are two aspects that I appreciate Corona ultra most: much better sensitivity (3 to 10 times better depending on the analyte) and superior RSD, which is very useful for quantitaitve analysis. Please see Figure 1 in the following link for proof data. http://www.dionex.com/en-us/webdocs/707 ... 239-02.pdf.

I found CAD about 5x lower LOD than Alltech 3500 and Sedex 85 but about 4x higher cost. 2nd poster said $25K
but I believe the current list for CAD is over $40K.

sorry I am using "£'" not "$'s" - always forget to clarify lol! £25k is probably roughly equivalent to about $40k?

lynz x